Continuous band-type power saws are in widespread use in the lumber and woodworking industry for many applications. For example, large saw mills use such band saws, pushing the logs lengthwise through the bands to obtain generally flatsided boards, planks, or other shapes.
Band saws used in saw mill applications usually operate at speeds varying generally from about 5,000 feet per minute to 10,000 feet per minute, according to the conditions of a particular application, such as the size of the saw and hardness of the wood being cut. To furnish the power required for cutting at such high speeds, the bands are customarily driven by large motor driven pulleys so that sufficient traction is obtained between the drive pulley and the band to prevent slippage under load conditions. Typical pulleys of the band saws found in saw mills have diameters on the order of six to ten feet. Because of the large mass inherent in pulleys of such large diameters, the rotational inertia of the pulleys resists acceleration and deceleration, requiring considerable time to get the pulleys up to speed and to stop them. The large diameter pulleys, of course, necessitate that the whole band saw machine be very large, which may be a distinct disadvantage in certain applications, especially when it is desired to make the saw mobile, or trailer-mounted for use in forests. One such application, in which a relatively small, light and mobile band saw is desirable is the shaping of trees for railroad ties which is commonly performed near the site where the trees are felled, often in tropical and subtropical locations where transportation of large heavy equipment may be difficult or even impossible.
Continuous band saws generally employ some type of transmission means, be it chains, belts, or gears, between the motor and drive pulley to transmit the rotary motion of the motor to that pulley. Such transmission means are subject to wear and require periodic servicing, both of which contribute to the expense and possibly downtime of the band saw. Even if the drive pulley is mounted directly on the motor shaft, however, the frictional drive contact between the pulley and band must be maintained in order to impart the rotary motion of the drive pulley to the band.
Band saws are also used in many applications other than saw mills, as in metalworking and woodworking shops and at construction sites. The difficulties and problems presented by a large band saw intended for mill use recur in the smaller saws used for these other applications, though on a somewhat reduced scale.